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A QUIET DRILL

April 25, 2003

The household and industrial heaters as well as glass and metal annealing furnaces are made of ordinary ceramics stand temperature difference poorly - the furnaces would crack as an common facetted glass where fiercely boiling water was pored in.

That is why the annealing furnaces have to be heated and cooled gradually and insensibly. It takes quite long to achieve the heating of 1300°Ãƒ' - about 4 to 8 hours, and it takes as long to get them cooled. After all, they do not get switched off - once heated, they are kept switched on even if there is no need in their continuous functioning.

That results in enormous wasteful power consumption. If the commonly used material is replaced by the material invented by the researchers from Chernogolovka, a location near Moscow, then the same furnace can be heated or cooled much quicker - in less then an hour.
An ordinary heater made of such ceramics can get heated within several seconds - to be more precise, within five seconds.

The most important element of a new composite is the silicon carbide matrix. It provides the entire composite with exceptional strength due to the fact that each silicon carbide grain in the mold is tied up with a similar grain and these bonds do not get broken until very high temperatures are acquired - actually, up to 2400°Ãƒ'. That makes the firm skeleton or framework of the entire material. However, it is practically impossible to get silicon carbide heated in ordinary conditions up to such temperature - it will simply burn down. To make their composites heat resistant, the researchers have suggested that silicides of refractory metals - molybdenum and tungsten - should be added to the compositions.

As a matter of fact, these silicides are stable to heating, i.e. they do not burn even at high temperatures. But, alas, they lose mechanical strength - when a rod of molybdenum and tungsten silicide is heated up to 1100°Ãƒ', it becomes soft as boiled macaroni, and if the temperature goes up to 1400°Ãƒ', the rod would stretch out like chewing gum under its own weight.

The new material consisting of silicon carbide and molybdenum silicide has inherited the best qualities from the 'parents'. In this composite the matrix of one component includes the grains of the other component - for example, the silicon carbide matrix contains the molybdenum silicide grains. As a result, silicides do not allow carbide to burn down, carbide in its turn, imparts the entire construction with high heat resistance up to 2000°Ãƒ'.

The scientists have ascertained that this extraordinary material possesses one more amazing quality. Not only does the material firmly resist the heating, it is capable of quick heating and cooling without cracking, i.e. the material can stand major temperature difference from the environment. This quality is normally expressed by the value of permissible specific thermal load. For instance, with ordinary nichrome heaters (practically all household heaters) the permissible specific thermal load makes only 2 W per square centimeter at 1100°Ãƒ', they burning down at higher temperatures. The new material possesses the value of 40-50 W per square centimeter and high strength even at 2000°Ãƒ'. Therefore, even a small heater made of new material will heat up the room quicker than an ordinary heater although its square is tens of times larger.

As for the holes in a concrete wall, the pin of the ceramics invented by the researchers from Chernogolovka can make a lot of holes quickly and, more importantly, absolutely quietly. One of the inventors, Boris Gnesin, senior research assistant, jokes that the main things when using such a pin is to avoid being too much carried away and burning the neighbors' carpet on the other side of the wall. However, the pin length can be regulated or selected in line with the dowel length. The point is that concrete gets soft already at 1600°Ãƒ', so the pin of new ceramics and heated up to 1800-2000°Ãƒ' can easily pierce through concrete making straight holes with smooth edges. This pin helps to avoid noise, dust and problems with the neighbors. In fact, there remains a circle (of several centimeters in diameter) scorched on the surface of the wall, but this cannot be considered high payment for protected nerves and good relations with the neighbors.

Informnauka (Informscience) Agency